1. Field of the Invention
The present invention relates generally to a capacitive stylus, and more particularly to a capacitive stylus for capacitive touch panel. In operation, the soft touch member of the stylus can keep a proper softness without being over-deformed or collapsed. Also, with the components of the capacitive stylus securely assembled with each other, the capacitive stylus has a good internal operation airflow system.
2. Description of the Related Art
Apple Computer, Inc, is one of the major suppliers of information products. In recent years, Apple Computer, Inc. has released various mobile phones and tablets employing capacitive touch panels. Such touch panel has a graphic operation interface supporting multipoint touch and is popularly accepted in the market. To catch up with the trend, many other manufacturers have also developed and released various information products with capacitive touch panels.
A capacitive touch panel has multiple electrodes uniformly distributed in two directions intersecting each other. When an external grounding conductor such as a finger or a stylus touches the capacitive touch panel, the self capacitance of the touched electrode and the mutual capacitance at the intersection will change. A necessary electrical signal reaction is achieved from the position of the changing electrode or intersection. Therefore, via the static current of the finger or the touch of the stylus, the touch position can be detected and calculated.
The touch operation interface basically is achieved by means of combining the touch panel with the graphic operation interface of the operation system. In operation of the capacitive touch screen, the signal actually flowing through the capacitive touch panel is very weak. Under some operation circumstances, the signal will be shifted due to the size and temperature of the finger or other factors. In this case, it is impossible to precisely and sensitively write a character or draft a graph and it is necessary to use a stylus instead of the finger.
At early stage, the capacitive stylus applied to the capacitive touch screen has a stylus stick made of conductive material with a certain length for conducting static of a user. A soft touch member basically made of conductive plastic or rubber is disposed at an end section of the stylus stick. A nib made of metal material in the form of a straight barrel is disposed in an internal hole of the end section of the stylus stick. The nib partially extends into the soft touch member. In generally, the soft touch member has a domed touch end for increasing contact area between the stylus and the capacitive touch panel and avoiding wear of the panel. The nib in the form of a straight barrel partially extends into the interior of the soft touch member. Under such circumstance, a considerably large gap exists between the nib and the soft touch member without any support. As a result, when a user uses the stylus to touch or slide on the capacitive touch screen, the center of the domed touch end of the soft touch member will be deformed and inward collapsed to an extent. In practice, the collapsed section will contact the capacitive touch screen by an insufficient area so that the sensation is poor. In this case, the touch position can be hardly precisely calculated. This will lead to shift of the touch position.
To overcome the above problem, for example, conventional skill discloses a stylus for capacitive touch screen. The stylus includes a copper column in the form of a straight barrel, which is assembled with an end section of the stylus stick and a soft conductive member disposed at the end section as a direct touch member. A nib is disposed between the copper column and the soft conductive member. The nib basically has a cross section in the form of a triangular pyramid. The nib can fully abut against an inner side of the bottom of the soft conductive member as a support structure for the touch end of the soft conductive member. The nib can avoid collapse of the soft conductive member in use. However, for achieving the necessary support effect, the components of such stylus are nearly totally tightly connected with each other without any internal airflow passage. This will affect the function of the stylus. Moreover, in such stylus, the soft conductive member, the copper column and the nib are not well electrically connected with each other.